Abstract In coastal regions and ocean areas, methanesulfonic acid (MSA; CH3SO3H) is present in considerable concentrations in the gas-phase and aerosols. It has been shown that MSA could contribute to growth and possibly form initial molecular cluster, which may lead to aerosol formation. However, quantitative concentrations and thermodynamic properties of MSA and sulfuric acid (SA; H2SO4) in the presence of water (W; H2O) remain largely uncertain. In this study, flow tube reactor was used to investigate the effects of each reactant on new particle formation (NPF) in a multi-component system consisting of MSA, SA, and W. Particles were measured for different combinations of reactants. It showed that a different order for reactant addition led to different experimental results, where the added MSA vapor to the SA-W binary system presented an obvious bimodal structure, for ternary system with SA added to the MSA-W, the similar bimodal phenomenon was not observed. The composition of clusters in the air flow was further analyzed by the commercial Atmospheric Pressure Interface Time-of-Flight Mass Spectrometer (APi-TOF-MS, Tofwerk AG), which is equipped with a homemade chemical ionization (CI) source, mass peaks corresponding to clusters that contain smaller MSA or SA molecules were clearly observed, indicating that these clusters are exist and stable. In addition, quantum chemistry calculation-based evaporation rate values were applied in a cluster dynamics model to yield formation rates of 2.6 × 102 cm−3 s−1 and cluster concentrations under different simulation conditions. This study could provide some insight into how acids interact in the atmosphere.

中文翻译：

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由甲磺酸和硫酸组成的大气分子簇的形成：来自流管实验和簇动力学模拟的见解

摘要 在沿海地区和海洋地区，甲磺酸（MSA；CH3SO3H）以相当高的浓度存在于气相和气溶胶中。已经表明 MSA 可能有助于生长并可能形成初始分子簇，这可能导致气溶胶形成。然而，MSA 和硫酸（SA；H2SO4）在水（W；H2O）存在下的定量浓度和热力学性质在很大程度上仍不确定。在本研究中，流动管反应器用于研究每种反应物对由 MSA、SA 和 W 组成的多组分系统中新粒子形成 (NPF) 的影响。测量不同反应物组合的粒子。结果表明，不同的反应物添加顺序会导致不同的实验结果，其中添加到SA-W二元体系中的MSA蒸气呈现出明显的双峰结构，对于添加到MSA-W中的SA的三元体系，没有观察到类似的双峰现象。气流中簇的组成由商用大气压力接口飞行时间质谱仪（APi-TOF-MS，Tofwerk AG）进一步分析，该质谱仪配备自制化学电离（CI）源，质量峰与含有较小 MSA 或 SA 分子的簇相对应，这表明这些簇是存在且稳定的。此外，基于量子化学计算的蒸发率值应用于簇动力学模型，以在不同的模拟条件下产生 2.6 × 102 cm-3 s-1 的形成速率和簇浓度。